1. Title of the Invention
The present invention relates to a slip control system for an automotive vehicle and, more particularly, to a slip control system for an automotive vehicle capable of preventing an excessive slip of the driven wheel of the automotive vehicle at the time of starting off or accelerating by adjusting or controlling torque applied to the driven wheels during running on the road having a low road surface friction coefficient .mu., such as frozen road.
2. Description of Related Art
U.S. Pat. No. 4,884,651 discloses technology in which torque for driving the wheels is decreased by decreasing output of the engine when a slip ratio of the driven wheel on a road surface reaches a predetermined value or higher in order to reduce torque for driving the wheels and allow the driven wheel to recover its grip, thereby suppressing the driven wheels from slipping.
A slip control system is known, which further comprises braking force controlling means for recovering a grip of the driven wheel having a slip ratio higher than the other driven wheel by braking the left-hand and right-hand driven wheels at different force, in addition to output controlling means of the engine, in order to effectively suppress the slip of the driven wheel.
Although such a slip control system as having the braking force controlling means for separately controlling the left-hand and right-had driven wheels, in addition to the output controlling means for controlling the output of the engine, presents the advantage that slip of the incipiently slipping driven wheel can be suppressed effectively, it suffers from the disadvantage that running stability of the automotive vehicle may be decreased due to an imbalance of the driving torque between the left-hand and right-hand driven wheel as a result of application of the braking force to the incipiently slipping driven wheel only, because control over the slip of the automotive vehicle is made only by the braking force controlling means when the output controlling means of the engine would cause an incident and the automotive vehicle would get out of control.